The present invention relates to a distance measuring method and a distance measuring apparatus. An input portion of the apparatus of the present invention forms a three dimensional image of an object and processes it, thereby obtaining distance data from the object to the lens. The input unit uses, for example, a television camera to form a two dimensional image of the object through a lens on a image focusing plane. More particularly this distance measuring method and distance measuring apparatus obtains distance data with ease using monocular vision based on two observed images with different blurs provided at positions which are different by a minute distance from each other along the same optical axis.
Several attempts for providing a distance measuring method have been made but a method similar to a human vision system has not been provided. Needs for such a computer vision system are very great in various industries. At present, the distance measuring methods used for an automatic apparatus require complicated techniques and structure. This is especially true when the distance measuring method is used as a computer vision system for an autonomous vehicle. It is necessary for the vehicle to instantaneously and automatically judge its outside situation in order to autonomously operate to a destination and to stop or avoid an obstacle in its way. The distance measuring method to be used for such an application needs to judge instantaneously with accuracy the distance up to an obstacle that has been detected on its path.
However, a method for obtaining complete distance image data has not been available. It is apparent that a visual sensor with distance sensitivity in three dimensional space like a human vision system is required by various industries.
Recently, a method of obtaining distance image data by performing computer processing of an image input from an image input apparatus such as a television camera has been utilized for visual inspection or control in the field of factory automation.
A method of measuring distance up to an object based on a principle of triangular measurement includes an image processing method of searching corresponding points between two input images of binocular vision by using a plurality of television cameras and measuring distances between the television cameras and the corresponding points, and parallax between the corresponding points.
On the other hand, a distance measuring method which does not use image processing, but measures distance up to an object by using a pointing device equipped with a laser has been widely used in the industrial field of public engineering works and architecture. A range sensor and a range finder for obtaining distance data based on two dimensional images by using laser scanning have been on the market.
The former method using image processing searches corresponding picture elements in each image based on a calculation by using an image input from at least two television cameras. For this method of utilizing a stereo view, a relative method or a dynamic programming method has been proposed for searching corresponding points.
However, although this method can recognize a situation in three dimensional space, this method requires a large amount of data as it scans the whole screen and, therefore, takes time to calculate distance data. This method especially takes much time to obtain the distance of a part such as at an edge at which the light and shade variation of the image is large and is easily affected by noise, thereby being unable to obtain complete distance image data.
The latter method not using image processing can extract two dimensional distance data but has the defects in that a high resolution of data is difficult and that it takes time to obtain three dimensional distance data.